The field of the invention relates generally to electrical control panels, and more specifically to fusible panelboards for electrical power systems.
Fuses are widely used as overcurrent protection devices to prevent costly damage to electrical circuits. Fuse terminals typically form an electrical connection between an electrical power source and an electrical component or a combination of components arranged in an electrical circuit. One or more fusible links or elements, or a fuse element assembly, is connected between the fuse terminals, so that when electrical current through the fuse exceeds a predetermined limit, the fusible elements melt and open one or more circuits through the fuse to prevent electrical component damage.
For power distribution purposes, fuses are sometimes arranged in and enclosed by a panelboard, sometimes referred to as a control panel. Other circuit protection components such as circuit breakers are also commonly used in combination with fuses in panelboards. A main service device connects a power supply to and from the panelboard, and the circuit breakers and fuses typically provide circuit protection to branch circuits being fed from the panel through the main disconnect. When the main service device is a disconnect switch it can be used to de-energize all the branch circuits, or the individual branch circuits can be de-energized using the circuit breakers while the main disconnect remains connected and the other branch circuits are still supplied with electrical power. Additionally, when electrical fault conditions occur, the circuit protectors (e.g., the breakers and the fuses) may be selectively coordinated so that only the affected branch circuit or feeder circuit may be interrupted while the other branch circuits and feeder circuits continue normal, full power operation.
For certain applications, circuit breakers tend to provide practical limitations on the current interruption ratings of such panelboards as well as practical limitations on the size of the panelboards. It would be desirable to provide smaller panelboards with higher interrupting ratings.